podman cgroup enhancement

currently, setting any sort of resource limit in a pod does nothing. With the newly refactored creation process in c/common, podman ca now set resources at a pod level
meaning that resource related flags can now be exposed to podman pod create.

cgroupfs and systemd are both supported with varying completion. cgroupfs is a much simpler process and one that is virtually complete for all resource types, the flags now just need to be added. systemd on the other hand
has to be handeled via the dbus api meaning that the limits need to be passed as recognized properties to systemd. The properties added so far are the ones that podman pod create supports as well as `cpuset-mems` as this will
be the next flag I work on.

Signed-off-by: Charlie Doern <cdoern@redhat.com>

vendor/github.com/opencontainers/runc/libcontainer/cgroups/fs2/defaultpath.go

@@ -0,0 +1,99 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package fs2
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/opencontainers/runc/libcontainer/configs"
+	"github.com/opencontainers/runc/libcontainer/utils"
+)
+
+const UnifiedMountpoint = "/sys/fs/cgroup"
+
+func defaultDirPath(c *configs.Cgroup) (string, error) {
+	if (c.Name != "" || c.Parent != "") && c.Path != "" {
+		return "", fmt.Errorf("cgroup: either Path or Name and Parent should be used, got %+v", c)
+	}
+
+	return _defaultDirPath(UnifiedMountpoint, c.Path, c.Parent, c.Name)
+}
+
+func _defaultDirPath(root, cgPath, cgParent, cgName string) (string, error) {
+	if (cgName != "" || cgParent != "") && cgPath != "" {
+		return "", errors.New("cgroup: either Path or Name and Parent should be used")
+	}
+
+	// XXX: Do not remove CleanPath. Path safety is important! -- cyphar
+	innerPath := utils.CleanPath(cgPath)
+	if innerPath == "" {
+		cgParent := utils.CleanPath(cgParent)
+		cgName := utils.CleanPath(cgName)
+		innerPath = filepath.Join(cgParent, cgName)
+	}
+	if filepath.IsAbs(innerPath) {
+		return filepath.Join(root, innerPath), nil
+	}
+
+	ownCgroup, err := parseCgroupFile("/proc/self/cgroup")
+	if err != nil {
+		return "", err
+	}
+	// The current user scope most probably has tasks in it already,
+	// making it impossible to enable controllers for its sub-cgroup.
+	// A parent cgroup (with no tasks in it) is what we need.
+	ownCgroup = filepath.Dir(ownCgroup)
+
+	return filepath.Join(root, ownCgroup, innerPath), nil
+}
+
+// parseCgroupFile parses /proc/PID/cgroup file and return string
+func parseCgroupFile(path string) (string, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+	return parseCgroupFromReader(f)
+}
+
+func parseCgroupFromReader(r io.Reader) (string, error) {
+	s := bufio.NewScanner(r)
+	for s.Scan() {
+		var (
+			text  = s.Text()
+			parts = strings.SplitN(text, ":", 3)
+		)
+		if len(parts) < 3 {
+			return "", fmt.Errorf("invalid cgroup entry: %q", text)
+		}
+		// text is like "0::/user.slice/user-1001.slice/session-1.scope"
+		if parts[0] == "0" && parts[1] == "" {
+			return parts[2], nil
+		}
+	}
+	if err := s.Err(); err != nil {
+		return "", err
+	}
+	return "", errors.New("cgroup path not found")
+}